1. Field of the Invention
The invention relates generally to electrical switching apparatus and, more particularly, to arc baffles for the arc chute assemblies of electrical switching apparatus, such as circuit breakers. The invention also relates to arc chute assemblies for electrical switching apparatus. The invention further relates to electrical switching apparatus employing arc chute assemblies.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, and abnormal level voltage conditions.
Circuit breakers, for example, typically include a set of stationary electrical contacts and a set of movable electrical contacts. The stationary and movable electrical contacts are in physical and electrical contact with one another when it is desired that the circuit breaker energize a power circuit. When it is desired to interrupt the power circuit, the movable contacts and stationary contacts are separated. Upon initial separation of the movable contacts away from the stationary contacts, an electrical arc is formed in the space between the contacts. The arc provides a means for smoothly transitioning from a closed circuit to an open circuit, but produces a number of challenges to the circuit breaker designer. Among them is the fact that the arc results in the undesirable flow of electrical current through the circuit breaker to the load. Additionally, the arc, which extends between the contacts, often results in vaporization or sublimation of the contact material itself. Therefore, it is desirable to extinguish any such arcs as soon as possible upon their propagation.
To facilitate this process, circuit breakers typically include arc chute assemblies which are structured to attract and break-up the arcs. Specifically, the movable contacts of the circuit breaker are mounted on arms that are contained in a pivoting assembly which pivots the movable contacts past or through arc chutes as they move into and out of electrical contact with the stationary contacts. Each arc chute includes a plurality of spaced apart arc plates mounted in a wrapper. As the movable contact is moved away from the stationary contact, the movable contact moves past the ends of the arc plates, with the arc being magnetically drawn toward and between the arc plates. The arc plates are electrically insulated from one another such that the arc is broken-up and extinguished by the arc plates. Examples of arc chutes are disclosed in U.S. Pat. Nos. 7,034,242; 6,703,576; and 6,297,465.
Additionally, along with the generation of the arc itself, ionized gases, which can cause excessive heat and additional arcing and, therefore, are harmful to electrical components, are formed as a byproduct of the arcing event. It is desirable to release such ionized gases in a safe manner which aids in the interruption of the electrical circuit. This involves cooling and de-ionizing the gases. To this end, it has been known to attempt to control the venting of the ionized gas by employing a filter or baffle structure at or about the arc chute, such as a screen, a labyrinth of protrusions or obstacles arranged to provide a predetermined gas passageway therethrough, and/or a baffle structure wherein one or more apertures of the structure is (are) variable or adjustable in size to control the flow rate of the ionized gases. However, there remains a very real and recognizable need for an improved mechanism for controlling and dissipating the ionized gases.
Accordingly, there is room for improvement in arc baffles for the arc chute assemblies, and in arc chute assemblies for electrical switching apparatus.